The present invention pertains to apparatus for treating articles of manufacture in a fluid. More particularly, the invention relates to doors and closures for treatment containers or barrels which are adapted to be disposed in a tank of treating fluid.
The invention finds particular application in the art of electroplating and will be described with particular reference thereto. However, it is to be appreciated that the invention is also applicable for cleaning, phosphating, rinsing and other treating operations.
A conventional plating barrel is filled with particulate workpieces or items to be plated or treated and immersed in an electroplating or other highly corrosive treating fluid. The barrel is rotated within a tank of treating fluid whereby the treated items cascade over each other in the interior of the barrel. The barrel interior is typically filled approximately one-third to one-half its capacity and generally holds workpieces collectively weighing over one hundred pounds and, on certain occasions, holding workpieces collectively weighing as much as five hundred pounds or more. The barrels must be sufficiently durable and are constructed of a material adapted to withstand the usually corrosive effects of the treating fluid. Selected plastics have been used with commerical success.
The barrel has a generally circular sidewall and a pair of opposed flat head ends or endwalls defining a work cavity therein. Oftentimes, the cylindrically shaped barrel is formed of a plurality of panel members arranged in a hexagonal or octogonal relationship and weldingly secured to the heads. One of the panels is left out of the welded arrangement and adapted or modified for selective removal and thereby function as a door. The removable panel provides ingress and egress to the interior work cavity. Due to the extreme weight and various workpiece sizes subject to the treating process, a secure and close fitting arrangement is required between the door and the remainder of the barrel. The enclosure mechanism which holds the door closed must be sufficiently strong to withstand the weight of the cascading workpieces contained therein, sufficiently corrosion resistant to withstand the treating fluids, and easy to operate.
By way of example, U.S. Pat. No. 2,886,505, issued May 12, 1959 to Singleton, et al. illustrates a conventional clamping arrangement for holding a door in a closed position. As is evident, the door is substantially similar to the remaining panels defining the sidewall of the generally cylindrical container. Still other clamping arrangements are illustrated in U.S. Pat. No. 912,041 to Snow and U.S. Pat. No. 2,843,979 to Lupo. Both of these patents require direct operator assistance in fastening and clamping the door in fixed, covering relation with the aperture and the remainder of the barrel. U.S. Pat. Nos. 3,507,529 and 3,583,739 issued Apr. 21, 1970 and June 8, 1971, respectively, to Gill are both directed to a door assembly for a plating barrel. Although applicable to use of automated machinery in lifting the door from the barrel, these arrangements necessarily require manual operator assistance to unfasten or remove the door from the opening. Even if adaptable to fully automated operation, the peripheral machinery necessary to unfasten and remove these doors from a barrel would be extremely complex and cost prohibitive.
One type of "hands-off" automatic door opening and closing apparatus for a barrel is exemplified in U.S. Pat. No. 3,861,654 issued Jan. 21, 1975 to Singleton. The door is designed for an arcuate movement between predetermined stop limits defining the door open and door closed postions. The type of structure illustrated by this patent has met with success. Nevertheless, it has been considered desirable to retain the benefits of a door which is recessed radially into the opening, as in the manual door arrangement, to prevent inadvertent sliding or falling out of the workpieces retained in the working cavity.
By way of example, electroplating small workpieces such as washers or the like requires close tolerances to be maintained between the door and aperture. If a washer were to become lodged between the edge of the door and the remainder of the container, the washer would fail to be properly electroplated or escape from the container. An increased focus on quality control could potentially lead to rejection of a large number of workpieces under such a scenario.
The present invention contemplates a new and improved door opening and closing apparatus for treatment barrels which provides an automatic "hands-off" operation along with the benefits of a close fitting recessed door arrangement.